Radionuclide distributions in Mediterranean coastal ecosystems as assessed by the concurrent analysis of marine sediments and macrophytes

Radionuclides, in relation to their radiological and environmental behaviour, may threaten marine ecosystems, where they undergo partitioning among water, sediments and biota, with potential transfer through food webs and spatial transports. Unfortunately, radionuclides are commonly neglected in monitoring of marine coastal ecosystems, especially of the Mediterranean Sea, where scant information is available not only on their activity in abiotic matrices, such as water and sediments, but also in sessile organisms such as macrophytes that may be potentially useful in biomonitoring applications. The present research aimed at investigating the spatial variations in the activity concentrations of natural and artificial radionuclides along the Tyrrhenian coast, evaluating their partitioning between sediments and macrophytes and the specific accumulation capabilities of the latter. Overall, 17 radionuclides were quantified: 7 Be, 40 K, 137 Cs, 208 Tl, 210 Pb, 210 Po, 212 Bi, 212 Pb, 214 Bi, 214 Pb, 224 Ra, 226 Ra, 232 Th (228 Ac), 235 U and 238 U (234 Th), with the major contribution to total marine radioactivity provided by 40 K, 210 Pb and 210 Po, and variable concentrations among the different species. In particular, brown algae such as Cystoseira spp. are able to accumulate a large variety of radionuclides and may represent good general biomonitors, whereas other species appear to be more selective towards specific radionuclides.